FIG. 1 shows a cross-sectional view of a conventional human tooth. The tooth consists of enamel (10), dentin (20), and pulp cavity (30), which are arranged in an inward order. Dentin (20) comprises hydroxyapatite and has a number of fine canals called dentin tubules (21) which connects the enamel (10) to the pulp cavity (30). The dentin tubules (21) are generally about two microns in diameter at their base and somewhat narrower at their periphery. Pulp cavity (30) has therein a nerve (31), blood vessels and lymphatic vessels. Dentin hypersensitivity (or also known as dentin sensitivity) is a common and uncomfortable condition caused by erosion of the enamel (10) exposing the hollow dentin tubules (21) thereby allowing external stimuli, such as for example, heat, cold, chemicals and physical and mechanical pressure or stimuli such as brushing to be able to irritate the nerves (31) through the open dentin tubules (21) resulting in pain sensation.
Some reports have dentin hypersensitivity affects up to 57% of patients worldwide (Addy M., Int. Dent. J., 2002: 52, 367-375). Due to its high prevalence rate, the oral care industry has developed oral care products for treating this condition. Common approaches to communicate the treatment effectiveness of these products, whether via live in-store presentation, on-line, print advertisement or television copy, rely on the use of demonstration tools such as for example animated videos (see, http://www.colgateprofessional.com/professional-education/videos/pro-argin-technology-mode-of-action) or magnified illustrations (FIG. 2). However, there are a number of challenges with these tools. Consumers tend to regard videos and images with skepticism because of the perception that they are not real-time and vivid representation of what is occurring, and therefore might have been visually enhanced to unfairly favor one product over the competition. Moreover, blown-up images are bulky and require a lot of space for display. They are also difficult to transport and are prone to being damaged during transport. Lastly, while animated videos might be able to show mode of action they cannot be readily used to measure and/or demonstrate treatment efficacy of products.
Accordingly, the need exists for an improved method and apparatus for assessing the treatment effectiveness of tooth sensitivity, preferably dentin hypersensitivity, with an oral care product. It is advantageous that the method and apparatus are easily transportable to various sites to be used in demonstrations to consumers. It is also advantageous that the method and apparatus are predictive of clinical effectiveness for treatment of tooth sensitivity. It is further advantageous that the method and apparatus of the present invention can be used as a quick screening tool for dentin hypersensitivity actives.